I know this might not fit here, but I need this for a game I’m making.

If you are referring to the platformer with the one eyed square cube I started seeing it around 2019/2020 and as far as I know its unknown who created it. If you are referring to basic platformers is general “Its hard to say because the first ”generic platformer“ wouldn't classify ”generic“ as it would of been the first of ”generic platformers".
The first platformer I could find is: Scrolling demonstration